my $schema = MyApp::Schema->connect(@DSN);
my $hash   = $schema->resultset("Hash");

my $good_key = "key";
say $hash->search({ $good_key => "foo" })->count;
##  executes: SELECT COUNT( * ) FROM hash me WHERE ( key = ? ): 'foo'
##  says 1

my $evil_key = "1 = 1 ) --";
say $hash->search({ $evil_key => "foo" })->count;
##  executes: SELECT COUNT( * ) FROM hash me WHERE ( 1 = 1 ) -- = ? ): 'foo'
##  says 3